Having failed to suppress this pagan festival in the Middle Ages, the Church was wise enough to adopt it as its own. The name carnival - from the Latin carne vale, "Goodbye to meat" - refers to the abstinence of Lent but has come to stand for the big blow-out of the day before. In some places this blow-out used to last all the way from Christmas day to Ash Wednesday; these days it is generally restricted to the days immediately before the Wednesday.
The traditional highlight of the feast was always the fatted cow - the Boeuf Gras - from which stems the name of Mardi Gras, or Fat Tuesday.
Despite the religious connotations, it is the pre-Christian elements underpinning the event that will be dominant this week. The wearing of masks and disguises is a direct throw-back to ancient Roman festivals in which social and sexual distinctions were temporarily over-ridden. With its emphasis on transvestism, erotic costumes, scantily clad dancers and flowing alcohol, the occasion has re-acquired more than a hint of its old Bacchanalian flavour.
The whole of the Catholic Mediterranean has been celebrating Carnival in its current form for centuries; the Nice Carnival for example dates back to the thirteenth century.
In Venice, where the atmosphere is less that of drunken revelry than of sophisticated intrigue, the carnival also has a long tradition. As well as harlequins and incognito strangers in black hoods and chalk white masks, the streets of Venice in the next couple of days will offer Renaissance madrigals, Commedia dell'Arte performances and puppet shows. On Tuesday night, participants from the local balls and neighbourhood parties will finally return to St Mark's Square for the ringing of bells at midnight to signal the end of the carnival and the beginning of Lent.
Carnival is a time when even the Germans throw off their reserve. In the city of Cologne, Weiberfastnacht ("women's carnival"), which took place last Thursday, is when women temporarily take control of the streets, running around town cutting off men's ties with scissors. Tomorrow, though, is Cologne's biggest day. Rose Monday will see a colossal parade of floats and giant figures, accompanied by hundreds of horses and possibly millions of spectators throwing sweets and bunches of flowers.
However, among the racially mixed communities across the Atlantic, carnival has taken on some even more bizarre, exaggerated forms. This weekend New Orleans is already an orgy of partying which is set to climax on Fat Tuesday, when massive parades, including the two most famous - Zulu and Rex - will pass though town. With the different krewes (parading groups) competing to parody each other more outrageously, as well as an insane amount of drinking, bead- flinging, flambeaux-carrying, chanting and other arcane traditions, this is by far the most anarchic party held in the United States each year.
At 2am tomorrow morning, local time, the greatest annual party in the Caribbean, that of Trinidad and Tobago, kicks off with the celebration known as Jouvert. In the pre-dawn hours, Ole mas revellers will take to the streets, dressed in creations of rags, mud and cast-off clothing. Steel bands with as many as 120 players - as well as giant DJ trucks with blaring speakers - begin delivering the calypso and soca music that will drive 48 hours of non-stop dancing.
The Brazilian Carnival, though, is surely the most spectacular street- party on Earth. In the days of slavery, masters adopted the custom of allowing their slaves to run freely for the three days prior to Ash Wednesday. This practice led to scenes of mad revelry that continued long after the abolition of slave-owning.
The most glittering single event in the whole pre-Lent celebration is the Samba School Parade in Rio de Janeiro. The samba schools taking part, each containing thousands of participants in fabulous costumes, are made up of poor people from the vast city slums. For many of these, the carnival is overwhelmingly the highlight of their year, if not their entire lives.
Britain celebrates, page 2
l Cologne. pounds 97 (to the end March) with Lufthansa or BA: German Travel Centre: 0181-429 2900. Eurostar: 0345 303030.
l Rio De Janeiro. From pounds 500. TAP 0171-839 1031; Iberia: 0171-830 0011; Journey Latin America: 0181- 747 8315
l Trinidad and Tobago. Charters from pounds 345; scheduled from pounds 539. Trailfinders: 0171 9375400.
l Venice. From pounds 150 (to 21 March) with Alitalia. Trailfinders: 0171- 937 5400